Small Asteroid or Comet 'Visits' from Beyond the Solar System

This animation shows the path of A/2017 U1, which is an asteroid -- or perhaps a comet -- as it passed through our inner solar system in September and October 2017. From analysis of its motion, scientists calculate that it probably originated from outside of our solar system. Credit: NASA/JPL-Caltech› Larger view

UPDATED on 11/15/17 at 9:15 am PST

The team from the Pan-STARRS observatory that was the first to detect the interstellar visitor has chosen the name 'Oumuamua for their discovery. The name is of Hawaiian origin and means a messenger from afar arriving first. Being the first known object of its type, the object also became the first to receive a new series designation from the International Astronomical Union (IAU), which assigns designations to astronomical objects. The IAU has announced the permanent designation of the interstellar object is "1I/2017 U1." In this first-of-its-kind IAU designation, the "I" stands for interstellar.

Original release issued Oct. 26, 2017

A small,
recently discovered asteroid -- or perhaps a comet -- appears to have
originated from outside the solar system, coming from somewhere else in our galaxy.
If so, it would be the first "interstellar object" to be observed and
confirmed by astronomers.

This unusual object - for now designated A/2017 U1 - is less than a quarter-mile (400 meters) in diameter and is moving remarkably
fast. Astronomers are urgently working to point telescopes around
the world and in space at this notable object. Once these data are obtained and
analyzed, astronomers may know more about the origin and possibly composition
of the object.

A/2017 U1 was discovered Oct. 19 by the
University of Hawaii's Pan-STARRS
1 telescope on Haleakala, Hawaii, during the course of its nightly search for near-Earth
objects for NASA. Rob Weryk, a postdoctoral researcher at the University of
Hawaii Institute for Astronomy (IfA), was first to identify the moving object
and submit it to the Minor Planet Center. Weryk subsequently searched the Pan-STARRS
image archive and found it also was in images taken the previous night, but was
not initially identified by the moving object processing.

Weryk immediately realized
this was an unusual object. "Its motion could not be explained using
either a normal solar system asteroid or comet orbit," he said. Weryk contacted
IfA graduate Marco Micheli, who had the same realization using his own
follow-up images taken at the European Space Agency's telescope on Tenerife in
the Canary Islands. But with the combined data, everything made sense. Said
Weryk, "This object came from outside our solar system."

"This
is the most extreme orbit I have ever seen," said Davide Farnocchia, a
scientist at NASA's Center for Near-Earth Object Studies (CNEOS) at the agency's
Jet Propulsion Laboratory in Pasadena, California. "It is going extremely
fast and on such a trajectory that we can say with confidence
that this object is on its way out of the solar system and not coming back."

The
CNEOS team plotted the object's current trajectory and even looked into its
future. A/2017 U1 came from the direction of the constellation Lyra, cruising
through interstellar space at a brisk clip of 15.8 miles (25.5 kilometers) per
second.

The object approached our solar system
from almost directly "above" the ecliptic, the approximate plane in
space where the planets and most asteroids orbit the Sun, so it did not have
any close encounters with the eight major planets during its plunge toward the
Sun. On Sept. 2, the small body crossed under the ecliptic plane just inside of
Mercury's orbit and then made its closest approach to the Sun on Sept. 9. Pulled by the Sun's
gravity, the object made a hairpin turn under our solar system, passing under
Earth's orbit on Oct. 14 at a distance of about 15 million miles (24 million
kilometers) -- about
60 times the distance to the Moon. It has now shot back up above the plane of the planets and, travelling
at 27 miles per second (44 kilometers per second) with respect to the Sun, the object
is speeding
toward the constellation Pegasus.

"We have long suspected that these objects should exist,
because during the process of planet formation a lot of material should be
ejected from planetary systems. What's most surprising is that we've never
seen interstellar objects pass through before," said Karen Meech, an
astronomer at the IfA specializing in small bodies and their connection to
solar system formation.

The small body has been assigned the temporary designation A/2017
U1 by the Minor Planet Center (MPC) in Cambridge, Massachusetts, where all observations on small bodies
in our solar system -- and now those just passing through -- are collected. Said MPC Director Matt Holman, "This kind
of discovery demonstrates the great scientific value of continual wide-field
surveys of the sky, coupled with intensive follow-up observations, to find
things we wouldn't otherwise know are there."

Since this is the first object of its type ever discovered,
rules for naming this type of object will need to be established by the
International Astronomical Union.

"We
have been waiting for this day for decades," said CNEOS Manager Paul
Chodas. "It's long been theorized that such objects exist -- asteroids or
comets moving around between the stars and occasionally passing through our
solar system -- but this is the first such detection. So far, everything
indicates this is likely an interstellar object, but more data would help to confirm
it."

The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS)
is a wide-field survey observatory operated by the University of Hawaii
Institute for Astronomy. The Minor Planet Center is hosted by the
Harvard-Smithsonian Center for Astrophysics and is a sub-node of NASA's Planetary
Data System Small Bodies Node at the University of Maryland (http://www.minorplanetcenter.net/ ). JPL hosts the Center
for Near-Earth Object Studies (CNEOS). All are projects of NASA's Near-Earth
Object Observations Program, and elements of the agency's Planetary Defense
Coordination Office within NASA's Science Mission Directorate.

More information about asteroids and near-Earth objects can be
found at: